Effective drug delivery to a patient is a critical aspect of any successful drug therapy. Of particular interest to the invention are pulmonary delivery techniques which rely on the inhalation of a pharmaceutical formulation by the patient so that a drug or active agent within the formulation can reach the lungs. Pulmonary delivery techniques can be advantageous for certain respiratory diseases in that it allows selective delivery of optimal concentrations of pharmaceutical formulations to the airways while causing less side effects than systematic administration. Nevertheless, many patients have experienced significant side effects caused by the necessary dosage for drugs commonly used in pulmonary delivery. Therefore, there is still a need to eliminate undesirable side effects, which in some case may include an increased risk for heart attack. For reducing these side effects, a pharmacologic approach has been taken. However, in some cases, the new found drugs are significantly more expensive thereby representing a major disadvantage to patients from poorer socioeconomic populations. Therefore, it would be advantageous to provide an alternative to the pharmacologic approach, whereby commonly used drugs can be delivered in an effective manner without the undesirable side effects.
It has been found that the efficacy of drug delivery can be improved by targeting the aerosolized medication to certain areas of the lungs. Delivery and deposition of aerosols are determined by both the aerosol characteristics and by patient's breathing characteristics. Many existing inhalation devices can deliver aerosolized particles to the lungs, yet lack the ability to target the delivery to certain areas of the lungs.
U.S. Pat. No. 5,906,202 describes a device and method for directing aerosolized mist to a specific area of the respiratory tract. By determining the particle size of the aerosols in combination with determining the volume of aerosol and aerosol free air allowed into the respiratory tract, it is possible for the described device to target a particular area of the respiratory tract. The device can allow the subject to inhale a predetermined volume of unaerosolized air followed by a predetermined volume of aerosol after which flow can be shut off completely or followed by additional aerosol free air. To this end, inspiratory flow rate measurements are made in order to determine a desired flow rate. The device then comprises a switch for releasing the predetermined volume of aerosol and aerosol free air at the desired flow rate. However, if the subject is unable to control their inspired flow rate to the set value, she/he will never receive the drug. This represents a disadvantage. It is also well known that the inspired flow can affect aerosol deposition independent of inspired volume. Since the described device requires that the subject breathe at a specific flow to trigger the aerosol, if the subject changes their flow immediately at the point of aerosol triggering, the deposition can be significantly altered, thereby representing another disadvantage. Further, there is still a need for a simpler device which enables lower costs for manufacture.